Plugged in a couple of heat belts and set them amidst a 4-some of carboys all wrapped up in a space blanket to promote a faster malolactic. They did the job, kept the temp 4-5 degrees C above ambient in the cellar for a month, but when I pulled them out, they and the towel they were sitting on were scorched, and the plastic on one had cracked open to reveal the heating wires (still insulated, mind you). Guess I got lucky on that little experiment in climate control. My basement has a nice wood floor to help spread the flames had they developed. Next time I'll go back to the more technical route. Stuff them in my garage freezer with a car warmer on a thermostat control.
Brian